Semiconductor micro-electromechanical (MEM) resonators, with quality factors (Q) often exceeding 104 can provide a high performance, low-power, compact CMOS-compatible alternative to electrical components in wireless communication and signal processing. The majority of electromechanical devices require a release step to freely suspend moving structures. This necessitates costly complex encapsulation methods and back end-of-line processing of large-scale devices. Development of *unreleased* Si-based MEMS resonators in CMOS allows seamless integration into Front End of Line processing with no post-processing or packaging.
In this talk, I will discuss the Resonant Body Transistor (RBT), which can be integrated into a standard CMOS process for low power clock generation and high-Q tank circuits. We recently demonstrated the first hybrid RF MEMS-CMOS resonators in Si at the transistor level of IBM’s SOI CMOS process, without the need for any post-processing or packaging. The unreleased, Si bulk acoustic resonators are driven capacitively using the thin gate dielectric, and actively sensed using a body-contacted nFET incorporated into the resonant cavity. FET sensing with the high fT, high performance transistors in CMOS amplifies the mechanical signal before the presence of parasitics. The resulting RF-MEMS resonators can provide low power, low cost, small footprint building blocks for on-chip signal generation and processing. For low loss and high power application, this concept can be extended to III-V semiconductors commonly used for mm-wave ICs (MMICs). I will discuss our latest results on active MEMS-HEMT resonators in GaN and their implications for channel-select radio design.